A combination of a boost converter which outputs a positive voltage and a buck-boost converter which outputs a negative voltage is to produce a positive output and a negative voltage output. It needs to have four low impedance power switches inside a chip. The disadvantage is that it requires two inductors, which will increase the cost of applications and occupy a larger PCB area. A combination of a boost converter which outputs a positive voltage and a charge-pump converter which outputs a negative voltage is to produce a positive output and a negative voltage output. This needs an inductor and a flying capacitor in applications. The disadvantage is a poorer load capacity of a negative voltage charge-pump and low efficiency. At the same time, an internal circuitry of a chip is more complex, inside of the chip, it needs to have six low impedance power switches, the cost of the chip is relatively higher. The flying capacitor is used to transfer an input energy to an output capacitor in a charge-pump; the power switch is a MOS transistor which is flowed through a larger current and acts as a switch.